Fastener driving tool

ABSTRACT

A tool comprising a drive-in element, transferring a fastening element into a substrate along setting axis by a setting energy E kin , a drive for driving the drive-in element along the setting axis, the drive comprising a capacitor, a rotor, and a coil, wherein current flows through the coil generating a magnetic field accelerating the drive-in element toward the fastening element, wherein a current intensity A coil  of current flowing through the excitation coil while discharging the capacitor has a time profile with a rising edge, a maximum current intensity A max  and a falling edge, A coil  rising during current rise time Δt rise  from 0.1 to 0.8 times A max  and during impact time Δt impact  is more than 0.5 times the A max , wherein Δt rise  is at least 0.020 ms and at most 0.275 ms and/or the impact time Δt impact  is at least 0.15 ms and at most 2.0 ms.

The present invention relates to a setting tool for driving fasteningelements into a substrate.

Such setting tools usually have a holder for a fastening element, fromwhich a fastening element held therein is transferred into the substratealong a setting axis. For this, a drive-in element is driven toward thefastening element along the setting axis by a drive.

U.S. Pat. No. 6,830,173 B2 discloses a setting tool with a drive for adrive-in element. The drive has an electrical capacitor and a coil. Fordriving the drive-in element, the capacitor is discharged via the coil,whereby a Lorentz force acts on the drive-in element, so that thedrive-in element is moved toward a nail.

The object of the present invention is to provide a setting tool of theaforementioned type with which high efficiency and/or good settingquality are ensured.

The object is achieved by a setting tool for driving fastening elementsinto a substrate, comprising a holder, which is provided for holding afastening element, a drive-in element, which is provided fortransferring a fastening element held in the holder into the substratealong a setting axis by a setting energy E_(kin), and a drive, which isprovided for driving the drive-in element toward the fastening elementalong the setting axis, wherein the drive comprises an electricalcapacitor, a squirrel-cage rotor arranged on the drive-in element and anexcitation coil, which during discharge of the capacitor is flowedthrough by current and generates a magnetic field that accelerates thedrive-in element toward the fastening element, wherein a currentintensity A_(coil) of the current flowing through the excitation coilduring the discharge of the capacitor has a time profile with a risingedge, a maximum current intensity A_(max) and a falling edge, whereinthe current intensity A_(coil) rises during a current rise timeΔt_(rise) from 0.1 times to 0.8 times the maximum current intensityA_(max) and during an impact time Δt_(impact) is more than 0.5 times themaximum current intensity A_(max), and wherein the current rise timeΔt_(rise) is at least 0.020 ms and at most 0.275 ms and/or the impacttime Δt_(impact) is at least 0.15 ms and at most 2.0 ms. The settingtool can in this case preferably be used in a hand-held manner.Alternatively, the setting tool can be used in a stationary orsemi-stationary manner.

In the context of the invention, a capacitor should be understood asmeaning an electrical component that stores electrical charge and theassociated energy in an electrical field. In particular, a capacitor hastwo electrically conducting electrodes, between which the electricalfield builds up when the electrodes are electrically chargeddifferently. In the context of the invention, a fastening element shouldbe understood as meaning for example a nail, a pin, a clamp, a clip, astud, in particular a threaded stud, or the like.

An advantageous embodiment is characterized in that the current risetime Δt_(rise) is at least 0.05 ms and at most 0.2 ms. A furtheradvantageous embodiment is characterized in that the impact timeΔt_(impact) is at least 0.2 ms and at most 1.6 ms.

An advantageous embodiment is characterized in that a maximum currentdensity in the excitation coil during the discharge of the capacitor isat least 800 A/mm² and at most 3200 A/mm².

An advantageous embodiment is characterized in that the capacitor andthe excitation coil are arranged in an electrical oscillating circuit,and wherein the capacitor has a capacitance C_(cap) and a capacitorresistance R_(cap), the excitation coil has a self-inductance L_(coil)and a coil resistance R_(coil) and the electrical oscillating circuithas a total resistance R_(total). A ratio of the capacitor resistanceR_(cap) to the total resistance R_(total) is preferably at most 0.6,particularly preferably at most 0.5. Likewise preferably, a ratio of theself-inductance LA to the coil resistance R_(coil) is at least 800 μH/Ωand at most 4800 μH/Ω. Likewise preferably, the capacitor has acapacitor time constant τ_(cap)=C_(cap) R_(cap) and the excitation coilhas a coil time constant τ_(coil)=L_(coil)/R_(coil), wherein a ratio ofthe coil time constant τ_(coil) to the capacitor time constant τ_(Cap)is at least 10, that is to say that the coil time constant τ_(coil) isat least 10 times the capacity time constant τ_(cap).

An advantageous embodiment is characterized in that the drive-in elementis provided for transferring a fastening element held in the holder intothe substrate with a setting energy E_(kin) of at least 30 J and at most600 J, wherein the drive-in element has a piston diameter d_(K) and apiston mass m_(K) and wherein, for the piston diameter d_(K)

⅔(a+b E _(kin) ^(n))≤d _(K)≤4/3(a+b E _(kin) ^(n))

where a=33 mm, b=6 mmJ^(−n) and n=⅓ and/or, for the piston mass m_(K),

⅔(c+d E _(kin) ^(n))≤m _(K)≤5/3(c+d E _(kin) ^(n))

where c=20 g, d=30 gJ^(−n) and n=⅓. In the context of the invention, thepiston diameter d_(K) should be understood as meaning the greatestextent of the drive-in element perpendicularly to the setting axis. Inthe case of a circular-cylindrical drive-in element or piston plate,this is the diameter of the cylinder.

The invention is represented in a number of exemplary embodiments in thedrawings, in which:

FIG. 1 shows a longitudinal section through a setting tool,

FIG. 2 shows a longitudinal section through an excitation coil,

FIG. 3 shows a time profile of a current intensity,

FIG. 4 shows an efficiency in dependence on a piston mass,

FIG. 5 shows a piston diameter in dependence on a setting energy and

FIG. 6 shows a piston mass in dependence on a setting energy.

FIG. 1 illustrates a hand-held setting tool 10 for driving fasteningelements into a substrate that is not shown. The setting tool 10 has aholder 20 formed as a stud guide, in which a fastening element 30 formedas a nail is held in order to be driven into the substrate along asetting axis A (to the left in FIG. 1). For the purpose of supplyingfastening elements to the holder, the setting tool 10 comprises amagazine 40 in which the fastening elements are held in storeindividually or in the form of a fastening element strip 50 and aretransported to the holder 20 one by one. To this end, the magazine 40has a spring-loaded feed element, not specifically denoted. The settingtool 10 has a drive-in element 60, which comprises a piston plate 70 anda piston rod 80. The drive-in element 60 is provided for transferringthe fastening element 30 out of the holder 20 along the setting axis Ainto the substrate. In the process, the drive-in element 60 is guidedwith its piston plate 70 in a guide cylinder 95 along the setting axisA.

The driving-in element 60 is, for its part, driven by a drive whichcomprises a squirrel-cage rotor 90 which is arranged on the piston plate70, an excitation coil 100, a soft-magnetic frame 105, a switchingcircuit 200 and a capacitor 300 with an internal resistance of 5 mOhm.The squirrel-cage rotor 90 consists of a preferably ring-like,particularly preferably circular ring-like, element with a lowelectrical resistance, for example made of copper, and is fastened, forexample soldered, welded, adhesively bonded, clamped or connected in aform-fitting manner, to the piston plate 70 on the side of the pistonplate 70 that faces away from the holder 20. In exemplary embodimentswhich are not shown, the piston plate itself is formed as asquirrel-cage rotor. The switching circuit 200 is provided for causingrapid electrical discharging of the previously charged capacitor 300 andconducting the thereby flowing discharge current through the excitationcoil 100, which is embedded in the frame 105. The frame preferably has asaturation flux density of at least 1.0 T and/or an effective specificelectrical conductivity of at most 10⁶ S/m, so that a magnetic fieldgenerated by the excitation coil 100 is intensified by the frame 105 andeddy currents in the frame 105 are suppressed.

In a ready-to-set position of the drive-in element 60 (FIG. 1), thedrive-in element 60 enters with the piston plate 70 a ring-like recess,not specifically denoted, of the frame 105 such that the squirrel-cagerotor 90 is arranged at a small distance from the excitation coil 100.As a result, an excitation magnetic field, which is generated by achange in an electrical excitation current flowing through theexcitation coil, passes through the squirrel-cage rotor 90 and, for itspart, induces in the squirrel-cage rotor 90 a secondary electricalcurrent, which circulates in a ring-like manner. This secondary current,which builds up and therefore changes, in turn generates a secondarymagnetic field, which opposes the excitation magnetic field, as a resultof which the squirrel-cage rotor 90 is subject to a Lorentz force, whichis repelled by the excitation coil 100 and drives the drive-in element60 toward the holder 20 and also the fastening element 30 held therein.

The setting device 10 further comprises a housing 110 in which the driveis held, a handle 120 with an operating element 130 which is designed asa trigger, an electrical energy store 140 which is designed as arechargeable battery, a control unit 150, a tripping switch 160, acontact-pressure switch 170, a means for detecting a temperature of theexcitation coil 100, which means is designed as a temperature sensor 180which is arranged on the frame 105, and electrical connecting lines 141,161, 171, 181, 201, 301 which connect the control unit 150 to theelectrical energy store 140, to the tripping switch 160, to thecontact-pressure switch 170, to the temperature sensor 180, to theswitching circuit 200 and, respectively, to the capacitor 300. Inexemplary embodiments which are not shown, the setting tool 10 issupplied with electrical energy by means of a power cable instead of theelectrical energy store 140 or in addition to the electrical energystore 140. The control unit comprises electronic components, preferablyinterconnected on a printed circuit board to form one or more controlcircuits, in particular one or more microprocessors.

When the setting tool 10 is pressed against a substrate that is notshown (on the left in FIG. 1), a contact-pressure element, notspecifically denoted, operates the contact-pressure switch 170, which asa result transmits a contact-pressure signal to the control unit 150 bymeans of the connecting line 171. This triggers the control unit 150 toinitiate a capacitor charging process, in which electrical energy isconducted from the electrical energy store 140 to the control unit 150by means of the connecting line 141 and from the control unit 150 to thecapacitor 300 by means of the connecting lines 301, in order to chargethe capacitor 300. To this end, the control unit 150 comprises aswitching converter, not specifically denoted, which converts theelectric current from the electrical energy store 140 into a suitablecharge current for the capacitor 300. When the capacitor 300 is chargedand the drive-in element 60 is in its ready-to-set position illustratedin FIG. 1, the setting tool 10 is in a ready-to-set state. Sincecharging of the capacitor 300 is only implemented by the setting tool 10pressing against the substrate, to increase the safety of people in thearea a setting process is only made possible when the setting tool 10 ispressed against the substrate. In exemplary embodiments which are notshown, the control unit already initiates the capacitor charging processwhen the setting tool is switched on or when the setting tool is liftedoff the substrate or when a preceding driving-in process is completed.

When the operating element 130 is operated, for example by being pulledusing the index finger of the hand which is holding the handle 120, withthe setting tool 10 in the ready-to-set state, the operating element 130operates the tripping switch 160, which as a result transmits a trippingsignal to the control unit 150 by means of the connecting line 161. Thistriggers the control unit 150 to initiate a capacitor dischargingprocess, in which electrical energy stored in the capacitor 300 isconducted from the capacitor 300 to the excitation coil 100 by means ofthe switching circuit 200 by way of the capacitor 300 being discharged.

To this end, the switching circuit 200 schematically illustrated in FIG.1 comprises two discharge lines 210, 220, which connect the capacitor300 to the excitation coil 200 and at least one discharge line 210 ofwhich is interrupted by a normally open discharge switch 230. Theswitching circuit 200 forms an electrical oscillating circuit with theexcitation coil 100 and the capacitor 300. Oscillation of thisoscillating circuit back and forth and/or negative charging of thecapacitor 300 may potentially have an adverse effect on the efficiencyof the drive, but can be suppressed with the aid of a free-wheelingdiode 240. The discharge lines 210, 220 are electrically connected, forexample by soldering, welding, screwing, clamping or interlockingconnection, to in each case one electrode 310, 320 of the capacitor 300by means of electrical contacts 370, 380 of the capacitor 300 which arearranged on an end side 360 of the capacitor 300 that faces the holder20. The discharge switch 230 is preferably suitable for switching adischarge current with a high current intensity and is formed forexample as a thyristor. In addition, the discharge lines 210, 220 are ata small distance from one another, so that a parasitic magnetic fieldinduced by them is as low as possible. For example, the discharge lines210, 220 are combined to form a busbar and are held together by asuitable means, for example a retaining device or a clamp. In exemplaryembodiments which are not shown, the free-wheeling diode is connectedelectrically in parallel with the discharge switch. In further exemplaryembodiments which are not shown, there is no free-wheeling diodeprovided in the circuit.

For the purpose of initiating the capacitor discharging process, thecontrol unit 150 closes the discharge switch 230 by means of theconnecting line 201, as a result of which a discharge current of thecapacitor 300 with a high current intensity flows through the excitationcoil 100. The rapidly rising discharge current induces an excitationmagnetic field, which passes through the squirrel-cage rotor 90 and, forits part, induces in the squirrel-cage rotor 90 a secondary electriccurrent, which circulates in a ring-like manner. This secondary currentwhich builds up in turn generates a secondary magnetic field, whichopposes the excitation magnetic field, as a result of which thesquirrel-cage rotor 90 is subject to a Lorentz force, which is repelledby the excitation coil 100 and drives the drive-in element 60 toward theholder 20 and also the fastening element 30 held therein. As soon as thepiston rod 80 of the drive-in element 60 meets a head, not specificallydenoted, of the fastening element 30, the fastening element 30 is driveninto the substrate by the drive-in element 60. Excess kinetic energy ofthe drive-in element 60 is absorbed by a braking element 85 made of aspring-elastic and/or damping material, for example rubber, by way ofthe drive-in element 60 moving with the piston plate 70 against thebraking element 85 and being braked by the latter until it comes to astandstill. The drive-in element 60 is then reset to the ready-to-setposition by a resetting device that is not specifically denoted.

The capacitor 300, in particular its center of gravity, is arrangedbehind the drive-in element 60 on the setting axis A, whereas the holder20 is arranged in front of the drive-in element 60. Therefore, withrespect to the setting axis A, the capacitor 300 is arranged in anaxially offset manner in relation to the drive-in element 60 and in aradially overlapping manner with the drive-in element 60. As a result,on the one hand a small length of the discharge lines 210, 220 can berealized, as a result of which their resistances can be reduced, andtherefore an efficiency of the drive can be increased. On the otherhand, a small distance between a center of gravity of the setting tool10 and the setting axis A can be realized. As a result, tilting momentsin the event of recoil of the setting tool 10 during a driving-inprocess are small. In an exemplary embodiment which is not shown, thecapacitor is arranged around the drive-in element.

The electrodes 310, 320 are arranged on opposite sides of a carrier film330 which is wound around a winding axis, for example by metallizationof the carrier film 330, in particular deposited by evaporation, whereinthe winding axis coincides with the setting axis A. In exemplaryembodiments which are not shown, the carrier film with the electrodes iswound around the winding axis such that a passage along the winding axisremains. In particular, in this case the capacitor is for examplearranged around the setting axis. The carrier film 330 has at a chargingvoltage of the capacitor 300 of 1500 V a film thickness of between 2.5μm and 4.8 μm and at a charging voltage of the capacitor 300 of 3000 V afilm thickness of for example 9.6 μm. In exemplary embodiments which arenot shown, the carrier film is for its part made up of two or moreindividual films which are arranged as layers one on top of the other.The electrodes 310, 320 have a sheet resistance of 50 ohms/sq.

A surface of the capacitor 300 is in the form of a cylinder, inparticular a circular cylinder, the cylinder axis of which coincideswith the setting axis A. A height of this cylinder in the direction ofthe winding axis is substantially the same size as its diameter,measured perpendicularly to the winding axis. On account of a smallratio of height to diameter of the cylinder, a low internal resistancefor a relatively high capacitance of the capacitor 300 and, not least, acompact construction of the setting tool 10 are achieved. A low internalresistance of the capacitor 300 is also achieved by a large line crosssection of the electrodes 310, 320, in particular by a high layerthickness of the electrodes 310, 320, wherein the effects of the layerthickness on a self-healing effect and/or on a service life of thecapacitor 300 should be taken into consideration.

The capacitor 300 is mounted on the rest of the setting device 10 in amanner damped by means of a damping element 350. The damping element 350damps movements of the capacitor 300 relative to the rest of the settingtool 10 along the setting axis A. The damping element 350 is arranged onthe end side 360 of the capacitor 300 and completely covers the end side360. As a result, the individual windings of the carrier film 330 aresubject to uniform loading by recoil of the setting tool 10. In thiscase, the electrical contacts 370, 380 protrude from the end surface 360and pass through the damping element 350. For this purpose, the dampingelement 350 in each case has a clearance through which the electricalcontacts 370, 380 protrude. The connecting lines 301 respectively have astrain-relief and/or expansion loop, not illustrated in any detail, forcompensating for relative movements between the capacitor 300 and therest of the setting tool 10. In exemplary embodiments which are notshown, a further damping element is arranged on the capacitor, forexample on the end side of the capacitor that faces away from theholder. The capacitor is then preferably clamped between two dampingelements, that is to say the damping elements bear against the capacitorwith prestress. In further exemplary embodiments which are not shown,the connecting lines have a rigidity which continuously decreases as thedistance from the capacitor increases.

FIG. 2 illustrates a longitudinal section through an excitation coil600. The excitation coil 600 comprises an electrical conductor,preferably made of copper, with a circular cross section, for example,which is wound in several turns 610 around a setting axis A₂. Overall,the excitation coil has a substantially cylindrical, in particularcircular-cylindrical, outer shape with an outside diameter R_(a) and acoil length L s_(p) in the direction of the setting axis A₂. In a regionthat is radially inner with respect to the setting axis A₂, theexcitation coil 600 has a free space 620, which is preferably likewisecylindrical, in particular circular-cylindrical, and defines an insidediameter R_(i) of the excitation coil 600. This results in aself-inductance of the coil of

$L_{Coil} = {\mu_{0}n_{W}^{2}\frac{r_{Sp}^{2}\pi}{L_{Sp} + {0.9\mspace{14mu} r_{Sp}}}}$

with the induction constant

${\mu_{0} = {4{\pi \cdot 10^{- 7}}\frac{Vs}{Am}}},$

a number n_(W) of the turns of the excitation coil 600 and an averagecoil radius r_(Sp)=½(R_(i)+R_(a)). Since the excitation coil 600 is in amagnetically saturated area during operation of the setting tool, thepermeability number μ_(r) of the excitation coil 600 is to be set asμ_(r)=1, so that the self-inductance can be calculated from the numberof turns and the dimensions of the excitation coil 600.

A means formed as a temperature sensor 660 for detecting a temperatureof the excitation coil 600 is arranged on an axial end face of theexcitation coil 600 with respect to the setting axis A₂ and is connectedin a thermally conducting manner to the excitation coil 600, for exampleby means of a thermal paste. In exemplary embodiments which are notshown, the temperature sensor is arranged on an inner circumference orouter circumference of the excitation coil.

FIG. 3 illustrates a time profile 400 of a current intensity A_(coil) ofa current flowing through an excitation coil during the discharge of acapacitor in a setting tool according to the invention. The currentintensity A_(coil) is given in amperes and is plotted against a time tinmilliseconds. The time profile 400 of the current intensity A_(coil) hasa rising edge 410, a maximum current intensity A_(max) of approximately6000 A and a falling edge 420. Within the rising edge 410, the currentintensity A_(coil) rises during a current rise time Δt_(rise) from 0.1times to 0.8 times the maximum current intensity A_(max). During animpact time Δt_(impact), the current intensity A_(Coil) is more than 0.5times the maximum current intensity A_(max).

In the present exemplary embodiment, the current rise time Δt_(rise) isapproximately 0.05 ms and the impact time Δt_(impact) is approximately0.4 ms. If the current rise time Δt_(rise) and the impact timeΔt_(impact) are chosen too small, the maximum current intensity A_(max)must be increased to ensure the same setting energy. However, thiscauses an increases in thermal load on the excitation coil and thus areduction in the efficiency of the drive. If the current rise timeΔt_(rise) and the impact time Δt_(impact) are chosen too large, thedrive-in element moves so far away from the excitation coil already inthe rising edge 410 that the repulsive force acting on the squirrel-cagerotor is reduced, which likewise lowers the efficiency of the drive.

With a cross-sectional area of the excitation coil of for example 3 mm²,a maximum current density in the excitation coil during the discharge ofthe capacitor is approximately 2000 A/mm². If the maximum currentdensity in the excitation coil is selected too low, the setting energythat can be achieved with an otherwise unchanged setting tool isreduced. To compensate for this, for example, the capacitor or theexcitation coil must be enlarged, which would however increase theweight of the setting tool. If the maximum current density in theexcitation coil is selected too high, a thermal load on the excitationcoil increases, with the result that the efficiency of the drive isreduced.

The capacitor and the excitation coil are arranged in an electricaloscillating circuit with a total resistance R_(total). The capacitor hasa capacitance C_(cap) and a capacitor resistance R_(cap). The excitationcoil has a self-inductance LA and a coil resistance R_(coil). A ratio ofthe capacitor resistance R_(Cap) to the total resistance R_(total) is0.14. If the ratio of the capacitor resistance R_(cap) to the totalresistance R_(total) is selected to be too large, a relatively largeamount of heat loss occurs in the capacitor, as a result of which theefficiency of the drive is reduced.

A coil time constant τ_(coil) of the excitation coil results from aratio of the self-inductance L_(coil) to the coil resistance R_(coil)and is for example 1000 μH/Ω or 1 ms. If the coil time constant τ_(coil)chosen too small, a current flow in the excitation coil increases tooquickly, which reduces the efficiency of the drive. If the coil timeconstant τ_(coil) is chosen too large, the current flow through theexcitation coil is distributed over a relatively great period of time.This results in a reduced maximum current intensity A_(max), whichreduces the efficiency of the drive.

In addition, the capacitor has a capacitor time constant τ_(cap)=C_(cap)R_(cap) and the excitation coil has a coil time constantτ_(coil)=L_(coil) R_(coil), wherein a ratio of the coil time constantτ_(coil) to the capacitor time constant τ_(cap) is approximately 150. Ifthe ratio of the time constants is chosen too small, a relatively largeamount of heat loss occurs in the capacitor, which reduces theefficiency of the drive.

FIG. 4 illustrates an efficiency 11 of a drive of a setting tool independence on a piston mass m_(K) of a drive-in element with a settingenergy E_(kin) of 125 J. The efficiency η has no unit, the piston massm_(K) is given in grams. A total efficiency η_(total) of the driveresults from a product of a recoil efficiency η_(R) and anelectromagnetic efficiency η_(em). The recoil efficiency η_(R) decreaseswith increasing piston mass m_(K), since, with the same setting energyE_(kin), an energy of a recoil of the setting tool increases withincreasing piston mass m_(K) and this recoil energy is lost. Theelectromagnetic efficiency η_(em) increases with increasing piston massm_(K), since, with the same setting energy E_(kin), an acceleration ofthe drive-in element decreases with increasing piston mass m_(K) andthus a length of time for the drive-in element in the area of influenceof the excitation coil increases. The piston mass m_(K) at which thetotal efficiency η_(total) of the drive is at a maximum can bedetermined as

m _(K)=(c+d E _(kin))

where c=20 g, d=30 gJ^(−n) and n=⅓. In the present example (E_(kin)=125J), the piston mass m_(K)=170 g.

FIG. 5 illustrates the relationship described above of the piston mass mK with the setting energy E_(kin). As described in connection with FIG.4, outside the range according to the invention, the total efficiencytotal of the drive decreases

⅔(c+d E _(kin) ^(n))≤m _(K)≤5/3(c+d E _(kin) ^(n))

significantly.

By analogy with FIG. 4, the recoil efficiency η_(R) also decreases withincreasing piston diameter d_(K), since, with increasing piston diameterd_(K), the piston mass m_(K) increases. Furthermore, the electromagneticefficiency η_(em) increases with increasing piston diameter d_(K),since, with increasing piston diameter d_(K), a diameter of thesquirrel-cage rotor increases, so that a repulsive force between theexcitation coil and the squirrel-cage rotor also increases. The pistondiameter d_(K) at which the total efficiency total of the drive is at amaximum for a given setting energy E_(kin) can be determined as

d _(K)=(a+b E _(kin) ^(n))

where a=33 mm, b=6 mmJ^(−n) and n=⅓. In the present example (E_(kin)=125J), the piston diameter d_(K)=63 mm.

FIG. 6 illustrates the relationship described above between the pistondiameter d_(K) and the setting energy E_(kin). As described above,outside the range according to the invention, the total efficiencyη_(total) of the drive decreases

⅔(a+b E _(kin) ^(n))≤d _(K)≤4/3(a+b E _(kin) ^(n))

significantly.

The invention has been described using a series of exemplary embodimentsthat are illustrated in the drawings and exemplary embodiments that arenot illustrated. The individual features of the various exemplaryembodiments are applicable individually or in any desired combinationwith one another, provided that they are not contradictory. It should benoted that the setting tool according to the invention can also be usedfor other applications.

1. A setting tool for driving fastening elements into a substrate,comprising a holder for holding a fastening element; a drive in elementfor transferring a fastening element held in the holder into thesubstrate along a setting axis by a setting energy E_(kin); and, a drivefor driving the drive-in element toward the fastening element along thesetting axis, wherein the drive comprises an electrical capacitor, asquirrel-cage rotor arranged on the drive-in element, and an excitationcoil; wherein current flows through the excitation coil during dischargeof the electrical capacitor and generates a magnetic field thataccelerates the drive-in element toward the fastening element, wherein acurrent intensity A_(coil) of the current flowing through the excitationcoil during the discharge of the electrical capacitor has a time profilewith a rising edge, a maximum current intensity A_(max) and a fallingedge, wherein the current intensity A_(coil) rises during a current risetime Δt_(rise) from 0.1 times to 0.8 times the maximum current intensityA_(max) and during an impact time Δt_(impact) is more than 0.5 times themaximum current intensity A_(max), and wherein the current rise timeΔt_(rise) is at least 0.020 ms and at most 0.275 ms and/or the impacttime Δt_(impact) is at least 0.15 ms and at most 2.0 ms.
 2. The settingtool as claimed in claim 1, wherein the current rise time Δt_(rise) isat least 0.05 ms and at most 0.2 ms and/or the impact time Δt_(impact)is at least 0.2 ms and at most 1.6 ms.
 3. The setting tool as claimed inclaim 1, wherein a maximum current density in the excitation coil duringthe discharge of the electrical capacitor is at least 800 A/mm² and atmost 3200 A/mm².
 4. The setting tool as claimed in claim 1, wherein theelectrical capacitor and the excitation coil are arranged in anelectrical oscillating circuit, and wherein the electrical capacitor hasa capacitance C_(cap) and an electrical capacitor resistance R_(cap),the excitation coil has a self-inductance L_(coil) and a coil resistanceR_(coil) and the electrical oscillating circuit has a total resistanceR_(total).
 5. The setting tool as claimed in claim 4, wherein a ratio ofthe electrical capacitor resistance R_(cap) to the total resistanceR_(total) is at most 0.6.
 6. The setting tool as claimed in claim 4,wherein a ratio of the self-inductance L_(coil) to the coil resistanceR_(coil) is at least 800 μH/Ω and at most 4800 μH/Ω.
 7. The setting toolas claimed in claim 4, wherein the electrical capacitor has anelectrical capacitor time constant τ_(cap)=C_(cap) R_(cap) and theexcitation coil has a coil time constant τ_(coil)=L_(coil)/R_(coil), andwherein a ratio of the coil time constant τ_(coil) to the electricalcapacitor time constant τ_(cap) is at least
 10. 8. The setting tool asclaimed in claim 1, wherein the drive-in element is provided fortransferring a fastening element held in the holder into the substratewith a setting energy E_(kin) of at least 30 J and at most 600 J,wherein the drive-in element has a piston diameter d_(K) and a pistonmass m_(K) and wherein, for the piston diameter d_(K)⅔(a+b E _(kin) ^(n))≤d _(K)≤4/3(a+b E _(kin) ^(n)) where a=33 mm, b=6mmJ^(−n) and n=⅓ and/or, for the piston mass m_(K),⅔(c+d E _(kin) ^(n))≤m _(K)≤5/3(c+d E _(kin) ^(n)) where c=20 g, d=30gJ^(−n) and n=⅓.
 9. The setting tool of claim 1, comprising a hand-heldsetting tool.
 10. The setting tool of claim 5, wherein the ratio ofR_(cap) to R_(total) is at most 0.5.
 11. The setting tool as claimed inclaim 5, wherein a ratio of the self-inductance LA to the coilresistance R_(coil) is at least 800 μH/Ω and at most 4800 μH/Ω.
 12. Thesetting tool as claimed in claim 5, wherein the electrical capacitor hasan electrical capacitor time constant τ_(cap)=C_(cap) R_(cap) and theexcitation coil has a coil time constant τ_(coil)=L_(coil)/R_(coil), andwherein a ratio of the coil time constant moil to the electricalcapacitor time constant τ_(cap) is at least
 10. 13. The setting tool asclaimed in claim 6, wherein the electrical capacitor has an electricalcapacitor time constant τ_(cap)=C_(cap) R_(cap) and the excitation coilhas a coil time constant τ_(coil)=L_(coil)/R_(coil), and wherein a ratioof the coil time constant moil to the electrical capacitor time constantτ_(cap) is at least
 10. 14. The setting tool as claimed in claim 2,wherein a maximum current density in the excitation coil during thedischarge of the electrical capacitor is at least 800 A/mm² and at most3200 A/mm².
 15. The setting tool as claimed in claim 2, wherein theelectrical capacitor and the excitation coil are arranged in anelectrical oscillating circuit, and wherein the electrical capacitor hasa capacitance C_(cap) and an electrical capacitor resistance R_(cap),the excitation coil has a self-inductance L_(coil) and a coil resistanceR_(coil) and the electrical oscillating circuit has a total resistanceR_(total).
 16. The setting tool as claimed in claim 3, wherein thecapacitor and the excitation coil are arranged in an electricaloscillating circuit, and wherein the electrical capacitor has acapacitance C_(cap) and an electrical capacitor resistance R_(cap), theexcitation coil has a self-inductance L_(coil) and a coil resistanceR_(coil) and the electrical oscillating circuit has a total resistanceR_(total).
 17. The setting tool as claimed in claim 15, wherein a ratioof the electrical capacitor resistance R_(cap) to the total resistanceR_(total) is at most 0.6.
 18. The setting tool as claimed in claim 16,wherein a ratio of the electrical capacitor resistance R_(cap) to thetotal resistance R_(total) is at most 0.6.
 19. The setting tool asclaimed in claim 15, wherein a ratio of the self-inductance L_(coil) tothe coil resistance R_(coil) is at least 800 μH/Ω and at most 4800 μH/Ω.20. The setting tool as claimed in claim 16, wherein a ratio of theself-inductance L_(coil) to the coil resistance R_(coil) is at least 800μH/Ω and at most 4800 μH/Ω.